Semiconductor devices need to be protected from electromagnetic waves emitted into the atmosphere from other products. For example, spark plugs firing in a car can create electromagnetic waves that adversely interfere with a microcontroller mounted under the hood of a car. Conventional packages do not protect the semiconductor devices within them from electromagnetic waves.
To prevent electromagnetic interference, groups of semiconductor devices are placed in a module or box. The module shields the semiconductor devices from electromagnetic interference (EMI). Even though using the module may provide overall EMI protection from outside interference, semiconductor devices inside the module can still interfere with each other. With low cost requirements and increased complexity of systems there is a need for a semiconductor packages themselves to shield electromagnetic waves so that the semiconductor devices can be placed in various parts of the car with or without a module. For example, to detect collisions from different directions appropriate sensors are located at various locations in the car. Furthermore, sensors without EMI protection cannot be grouped in the same module with other semiconductor devices if the latter produce EMI. It becomes costly to place each sensor in an individual module for electromagnetic protection.
One solution to prevent electromagnetic interference is to place a metal cap over a semiconductor device prior to molding the package. This solution is only applicable to ball grid array (BGA) packages which encapsulate a large semiconductor die (i.e., at least one inch squared). Therefore, a need exists for a solution for component level EMI shielding that can be used in a variety of packages with any semiconductor die size.
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